1. Field of the Invention
The present invention relates to an improved electrical de-icer for heating an ice accumulation surface of an aircraft to control ice accumulation on a structural member, and more particularly to a de-icer facilitating heat flow between adjoining elements.
2. Description of the Prior Art
The accumulation of ice on aircraft wings and other structural members in flight is a danger that is well known. As used herein, the term "structural members" is intended to refer to any aircraft surface susceptible to icing during flight, including wings, stabilizers, engine inlets, rotors, and so forth. Attempts have been made since the earliest days of flight to overcome the problem of ice accumulation. While a variety of techniques have been proposed for removing ice from aircraft during flight, these techniques have had various drawbacks that have stimulated continued research activities.
One approach that has been used is so-called thermal deicing. In thermal de-icing, the leading edges, that is, the portions of the aircraft that meet and break the airstream impinging on the aircraft, are heated to prevent the formation of ice or to loosen accumulated ice. The loosened ice is blown from the structural members by the airstream passing over the aircraft.
In one form of thermal de-icing, heating is accomplished by placing an electrothermal pad(e), including heating elements, over the leading edges of the aircraft, or by incorporating the heating elements into the structural members of the aircraft. Electrical energy for each heating element is derived from a generating source driven by one or more of the aircraft engines. The electrical energy is intermittently or continuously supplied to provide heat sufficient to prevent the formation of ice or to loosen accumulating ice.
With some commonly employed thermal de-icers, the heating elements are configured as ribbons, i.e. interconnected conductive segments, that are mounted on a flexible backing. The conductive segments are separated from each other by gaps, i.e. intersegmental gaps, and each ribbon is electrically energized by a pair of contact strips. When applied to a wing or other airfoil surface, the segments are arranged in strips or zones extending spanwise or chordwise of the aircraft wing or airfoil. One of these strips, known as a spanwise parting strip, is disposed along a spanwise axis which commonly coincides with a stagnation line that develops during flight in which icing is encountered. Other strips, known as chordwise parting strips, are disposed at the ends of the spanwise parting strip and are aligned along chordwise axes. Other zones, known as spanwise shedding zones, typically are positioned above and below the spanwise parting strip at a location intermediate the chordwise parting strips. Between adjacent zones, a gap, known as an interheater gap, exists.
In one preferred form of de-icing, an electrical current is transmitted continuously through the parting strips so that the parting strips are heated continuously to a temperature above 32.degree. F. In the spanwise shedding zones, on the other hand, current is transmitted intermittently so that the spanwise shedding zones are heated intermittently to a temperature above about 32.degree. F. While this technique of heating the various zones generally is effective to melt ice (or prevent its formation) without the consumption of excessive current, a problem exists in that melting of ice in the inter-segmental and interheater gaps can be difficult or impossible. Moreover melting of ice on or around the contact strips can also be difficult or impossible. Accumulation of ice in the gaps and on the contact stripe is particularly undesirable since the unmelted ice serves as "anchors" for ice that would be melted but for the ice accumulated in the gaps or on the contact strips.
Desirably, a thermal de-icer would be available that would provide effective de-icing action while employing an efficient design that minimizes the formation of cold spots.